1. Field
The present inventive concept relates to nonvolatile memory devices, and more particularly, to nonvolatile memory devices having a three dimensional structure having high integration without increasing a size of a cell array.
2. Description of the Related Art
Generally, nonvolatile memory devices can electrically erase and program data, and can retain their stored data even when their power supplies are interrupted. For this reason, the nonvolatile memory devices are being widely used in various fields.
Nonvolatile memory devices include various types of memory cell transistors and are classified into a NAND-type and a NOR-type according to a cell array structure. A NAND-type nonvolatile memory device has an advantage of high integration and a NOR-type nonvolatile memory device has an advantage of high speed.
In particular, since the NAND-type nonvolatile memory device has a cell string structure serially connecting a plurality of memory cell transistors, it provides the advantage of high integration. Also, since the NAND-type nonvolatile memory device adopts an operation method of simultaneously changing data stored in a plurality of memory cell transistors, a speed of updating data is high compared with the NOR-type nonvolatile memory device. The NAND-type nonvolatile memory device is mainly used in a portable device which requires a mass storage device such as a digital camera or a MP3 player because of high integration and high speed of updating data.
Studies for promoting and improving the advantages of the NAND-type nonvolatile memory device have been performed and as a part of these studies, NAND-type nonvolatile memory devices having three dimensional structures have been developed.